Slide rule attachment



Dec. 6, 1949 J. J. SMIDL 2,490,240

SLIDE RULE ATTACHMENT Filed March 4, 1949 .Z Z I 6 1 f /0 2 INVENTOR.Joseph J. 5m id! H W Mm flffurnsy Patented Dec. 6, 1949 UNITED STATESPATENT OFFICE SLIDE RULE ATTACHMENT Joseph J. Smidl, Portland, Oreg.Application March 4, 1949, Serial No. 79,638

6 Claims. 1

The present invention comprises a characteristic accumulator forassociation with a slide rule, the purpose of the invention being toprovide means whereby the operator of a slide rule may accumulatecharacteristic figures at each operation of a series of mathematicalcomputations performed upon the slide rule so that he may be constantlyaware of the size of the accumulated resultant. It is well known thatthe operation of a slide rule requires constant attention to the sizesof the various numerals being multiplied or divided. Usually theoperator follows the operations mentally; and this is a frequent sourceof serious errors in slide-rule computing. If a large number of numeralsare being multiplied together or divided into each other, or thecalculation requires a mixture of multiplying and dividing operations,the operator may be required to keep a work chart wherein he roughlycomputes the size of the resultant. These computations require time andextra effort and must be carefully attended to in order to avoidinaccuracies. The object of the present invention is to relieve theoperator of excessive mental or manual effort in determining the propersizes of the resultants of complicated mathematical operations by pro=vidin means for accumulating the characteris tic figures as eachoperation of a series is performed upon the slide rule.

The present invention is, in one sense, an adding machine, since itprovides means whereby each operation of a manually engageable partresults in the algebraic addition of the numeral one to a previouslyaccumulated characteristic total. If an operation is such as to increasethe characteristic by more than one an addition lever may be operatedmore than once, and if the operation results in the subtraction of morethan one from the accumulated total characteristic a subtraction levermay be operated more than once. The principle of the foregoing isembodied in my prior patent, No. 2,418,910, issued April 15, 1947, forwhich application for reissue, Serial No. 70,421, was filed on December30, 1948, and which was reissued as Re. 23,127 on June 21, 1949. In thatpatent the principle is embodied in a cursor for a slide rule. Thepresent invention comprises a structure which may be attached to theslide rule and over which an enlarged cursor of the regular type maybefitted. The present embodiment of the invention has the advantage thatthe operating levers project beyond the ends of the slide rule inposition to be readily engageable Without releasin the slide rule,whereas with the embodiment illustrated and described in the priorpatent it is usually necessary for the operator to release the sliderule with one or the other hand in order to engage the operating leversof the characteristic accumulator. The present invention has the furtheradvantage over the prior form in that the addition lever is always foundin the same position at one end of the slide rule and the subtractionlever is always found in a cor-- responding position at the other end ofthe slide rule, so that the operation thereof becomes automatic throughhabitual use, whereas with the prior form it is necessary to move thehand to the position the cursor happens to occupy at the time whilementally guarding against operating one lever when it was intended thatthe other should be operated.

An object of the present invention is to provide a device of thecharacter described which is easily formed of relatively few, sturdy andeasily manufactured and assembled parts.

The objects and advantages of the present in vention will be morereadily understood by inspection of the following specification taken inconnection with the accompanying drawing wherein like numerals refer tolike parts throughout, while the features of novelty will be moredistinctly pointed out in the appended claims.

In the drawing Fig. 1 is a plan view of the present invention, withparts broken away, the invention being shown attached to a skeletonizedslide rule and embraced by a skeletonized cursor mounted on the sliderule;

Fig. 2 is a side view of the invention taken from the plane of the line22 of Fig. 1;

Fig. 3 is a partial view of the invention, on an enlarged scale, takenfrom the line 3--3 of Fig. 1;

Fig. 4 is a section through the invention taken along the line 44 ofFig. 2;

Fig. 5 is a partial view similar to Fig. 4 showing the parts in anotherposition at the end of an operative movement;

Fig. 6 is an end view of the invention shown in its position ofattachment to a slide rule;

Fig. 7 is a section, on an enlarged scale, taken along line 1! of Fig.5; and

Fig. 8 is a vertical section taken along line 8-8 of Fig. 5.

The preferred form of the invention comprises a channel-shaped housingincluding an outer channel-shaped member I!) and an inner channel shapedmember I I the two members being spaced apart by a strap I2 at each endthereof, the legs of each strap extending beyond the channelshapedmembers to provide ears I3 through which a bolt M may be passed. Theears are set into depressions in the upper and lower graduated surfacesof the slide rule and the bolt passed through an opening through theslide rule. By such an arrangement the channel-shaped housing ispositioned along one of the narrow longitudinal surfaces of the sliderule with its flanges directed toward the edges of the slide rulewhereby the outer surfaces of the flanges form extensions of thegraduated surfaces of the slide rule. In order that the channel membersand the straps I2 may be held together, the same are united by rivetsI5. Preferably the heads of the bolts I4, and the nuts thereon, are verythin and the rivets I5 are inset so as not to interfere with theoperation of the usual cursor. The structure described provides a hollowspace adjacent a narrow longitudinal edge of the slide rule enclosed bya double wall housing providing a channel-shaped space l6 extending theentire length of the slide rule except for the small portions blockedoff by the straps I2.

A runner is mounted in the channel-shaped space, the same preferablybeing channel-shaped so as to have flanges 28, the bottom of the runnerbeing provided with a plurality of evenly spaced openings separated bynarrow straps 2I extending across the bottom of the channel-shapedspace, the runner therefore being substantially a rack, or a memberhaving a plurality of abutments evenly spaced longitudinally thereof.The runner is no greater in length than one-half of the length of thechannel-shaped space I6 so that a central point of the runner may bedisplaced one-half of its length toward either end of the space It froma centered position. At least one of the flanges of the outer member I8is provided with a window 22 at the longitudinal center thereof, and atleast one of the flanges 28 is provided with a plurality of evenlyspaced characteristic indicia 23 in position to be viewed through thewindow 22. As seen in Fig. 1, the characteristic indicia 23 preferablycomprise a Zero, which is located at the longitudinal center of therunner, a series of ascending positive numerals extending from the zerotoward the right end of the runner, and a series of ascending negativenumerals extending from the zero toward the left end of the runner. Theindicia 23 are of such size as to be viewed singly through the window 22and are evenly spaced along the flange of the runner, the spacingthereof preferably being equal to the spacing of the connecting straps2I.

A pair of operating levers or bars are provided, the same comprising afirst, or addition, bar 24 extending from the right end of the housingand a second, or subtraction, bar 25 extending from the left end of thehousing, each bar being preferably providedwith an angularly directedtip so as to provide a flat surface for engagement with the tip of afinger. Since each bar and its associated parts is identical, only one,namely the second bar, is herein fully illustrated and described.

The bar 25 is slidably mounted within the channel-shaped housing, beingretained against the bottom of the inner member Ii by a pair of U-shaped straps 26 and 21, the straps being retained in position by rivets28 and 29 respectively, extending across the housing to brace thestructure. The bar 25 is slidable longitudinally of the housing betweenthe bottom of the inner member II and the bottoms of the U-shapedstraps. The bar 4 is normally urged outwardly by a spring 30 hooked overthe rivet 28 and having its other end attached to a screw 3| extendinginwardly from the lower surface of the bar. The bar is limited in itsoutward movement by engagement of the bottom of strap 27 with the outerend of a pawl 32 mounted upon the inner end of the bar. The pawl ismounted upon the bar by a screw 33 passing through an enlarged openingin the outer end of the pawl into the bar and a second screw 34 passingthrough a second enlarged opening in the inner end of the pawl into thetip of the bar. A spring 35 is positioned between the head of screw 34and the pawl so as constantly to urge the pawl toward the bottom of thechannel-shaped housing. The tip of the pawl projects outwardly towardthe connecting straps 2| so that, when permitted to do so, it may engageone of the straps whereby the runner may be moved longitudinally uponcontinued movement of the operating bar. In order to permit suchengagement the bottom of the channel member I I is provided with anopening 36, the opening being of such length that when the bar isprojected outwardly to its limit of movement the dog 32 is cammed intothe housing by a cam surface thereof engaging the outer end of theopening 36. On the other hand, when the operating bar is moved inwardlythe pawl may enter one of the openings between a pair of straps 2|,thereby to engagecne of the straps and move the runner, the opening 36being of such length as to limit movement of the runner to the distancerequired to displace one characteristic index with an adjacentcharacteristic index, the movement being limited by the pawl engagingthe inner end of the opening 36. In Fig. 4 the opposed opening 3? isillustrated, this opening being identical to opening 36 and beingprovided for the purpose of permitting operation of a pawl 38 (Fig. 8)identical to pawl 32 and mounted upon the addition lever 24 in theidentical manner as the first pawl is mounted upon the subtractionlever.

The operation is illustrated in Figs. 4 and 5. In Fig. 4 the pawl 32 isshown in withdrawn position in full line and in projected position indotted line just before it engages one of the cross straps. In Fig. 5the pawl is illustrated in the position at which further movement of therunner is limited by the pawl engaging the inner end of the opening 36.

The operation of the device is relatively simple and easily understood.Upon each inward movement of the addition bar 24 the runner is displacedtoward the left by the distance between adjacent characteristic indicia,and upon each inward movement of the subtraction bar 25 the runner isdisplaced one characteristic toward the right. Therefore, if anoperation of the slide rule requires increasing or reducing theaccumulated characteristic by more than one, the appropriate bar isoperated the appropriate number of times before the next operation ofthe slide rule. Therefore, any characteristic, either negative orpositive, within the limits of size of the runner, may be accumulated,with the result being viewable through the window 22.

It is obvious that the opposite surface of the outer member ID mayhave awindow therein and the opposite flange 20 of the runner may have indiciathereon. Likewise, the window may be of such length as to permit viewingof more than one of the indicia, in which case it would be necessary toprovide a cross-hair or reference mark to locate the resultant of aseries of operations. A window of the size shown is preferable so as toavoid the appearance of confusing numerals on the accumulator. Othermodifications in arrangement and detail will be readily apparent tothose skilled in the art, and I claim as my invention all suchmodifications as come within the true spirit and scope of the appendedclaims.

I claim:

1. A characteristic accumulator for association with a slide rulecomprising an elongated, channel-shaped housing adapted to be attachedto a slide rule along one of the narrow longitudinal surfaces thereofwith its flanges directed toward the edges of the slide rule whereby theouter surfaces of said flanges form extensions of the graduated surfacesof the slide rule, said housing comprising inner and outer membersspaced from each other to provide an enclosed space, a runner slidablyretained in said space and comprising a plurality of abutments evenlyspaced longitudinally thereof, said space being at least twice as longas said runner, said runner having evenly spaced characteristic indiciathereon and the outer member of said housing having a window thereinthrough which said indicia may be viewed, a first bar slidably mountedfor longitudinal movement in said housing and including a manuallyengageable portion projecting from one end thereof, a second barslidably mounted for lon gitudinal movement in said housing andincluding a manually engageable portion projecting from the opposite endthereof, spring means in said housing urging said bars outwardly, meanslimiting outward movement of said bars, a first pawl mounted on saidfirst bar and engageable with said abutments upon inward movement ofsaid first bar, a first spring constantly urging said pawl toward saidabutments, first retracting means to retract said first pawl from saidabutments upon outward movement of said first bar to its limit ofmovement, first inward movement limiting means to limit movement of saidrunner in one direction upon each inward movement of said first bar tothe amount required to displace one characteristic index with anadjacent characteristic index, a second pawl mounted on said second barand engageable with said abutments upon inward movement of said secondbar, a second spring constantly urging said second pawl toward saidabutments, second retracting means to retract said second pawl from saidabutments upon outward movement of said second bar to its limit ofmovement, and second inward movement limiting means to limit movement ofsaid runner in the opposite direction upon each inward movement of saidsecond bar to the amount required to displace one characteristic indexwith an adjacent characteristic index.

2. The structure set forth in claim 1 wherein said characteristicindicia comprise a series of positive numerals arranged in ascendingorder in one direction from a zero located at the 1ongitudinal center ofthe runner and a series of negative numerals ranging in ascending orderin the opposite direction from said zero.

3. The structure set forth in claim 1 in which said window is of suchsize as to permit viewing of one only of said characteristic indicia andsaid window is located at the longitudinal center of said housing.

4. A characteristic accumulator for association with a slide rulecomprising an elongated, channel-shaped housing adapted to be attachedto a slide rule along one of the narrow longitudinal surfaces thereofwith its flanges directed toward the edges of the slide rule whereby theouter surfaces of said flanges form extensions of the graduated surfacesof the slide rule, said housing comprising inner and outer membersspaced from each other to provide an enclosed channel-shaped space, achannel-shaped runner slidably retained in said space and having apluralit of evenly spaced openings in the bottom thereof providing aplurality of ahiitments evenly spaced longitudinally thereof, said spacebeing at least twice as long as said runner, said runner having evenlyspaced characteristic indicia on at least one flange thereof the outermember of said housing having a window in at least one flange thereofthrough which said indicia may be viewed, 9, first bar slidably mountedfor longitudinal movement in said housing and including a manuallyengageable portion projecting from one end thereof, a second barslidably mounted for longitudinal movement in said housing and includinga manually engageable portion projecting from the opposite end thereof,spring means in said housing urging said bars outwardly, means limitingoutward movement of said bars, the inner member of said housing having apair of openings in the bottom thereof, a first pawl mounted on saidfirst bar and engageable with said abutments through one of saidopenings upon inward movement of said first bar, a first springconstantly urging said pawl toward said abutments, the outer edge ofsaid opening operating to retract said first pawl from said abutmentsupon outward movement of said first bar to its limit of movement and theinner edge of said opening engaging said pawl to limit movement of saidrunner in one direction upon each inward movement of said first bar tothe amount required to displace one characteristic index with anadjacent characteristic index, a second pawl mounted on said second barand engageable with said abutments through the other of said openingsupon inward movement of said second bar, and a second spring constantlyurging said second pawl toward said abutments, the outer edge of saidother opening operating to retract said second pawl from said abutmentsupon outward movement of said second bar to its limit of movement andthe inner edge of said other opening engaging said second pawl to limitmovement of said runner in the opposite direction upon each inwardmovement of said second bar to the amount required to displace onecharacteristic index with an adjacent characteristic index.

5. The structure set forth in claim 4 wherein said characteristicindicia comprise a series of positive numerals arranged in ascendingorder in one direction from a zero located at the longitudinal center ofthe runner and a series of negative numerals ranging in ascending orderin the opposite direction from said zero.

6. The structure set forth in claim 4 in which said window is of suchsize as to permit viewing of one only of said characteristic indicia andsaid window is located at the longitudinal center of said housing.

JOSEPH J. SMIDL.

No references cited.

